What are cowl flaps?

[Mxsmanic]

What are cowl flaps for, and how are they used? The name implies that
they are some sort of aerodynamic control surface, but they don't
appear to have any aerodynamic effects. In simulation, they are doors
on the bottom of the engine nacelles that open for some unclear
purpose (I see what looks like exhaust pipes or something inside).
What do they do, and why do I have a control for opening and closing
them? This is on a Baron 58, the aircraft I usually fly in
simulation.

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[Gary Drescher]

"Mxsmanic" > wrote in message
...
> What are cowl flaps for, and how are they used? The name implies that
> they are some sort of aerodynamic control surface, but they don't
> appear to have any aerodynamic effects. In simulation, they are doors
> on the bottom of the engine nacelles that open for some unclear
> purpose (I see what looks like exhaust pipes or something inside).
> What do they do, and why do I have a control for opening and closing
> them? This is on a Baron 58, the aircraft I usually fly in
> simulation.

http://stoenworks.com/Tutorials/Cowl%20Flaps%20&%20Engine%20C.html

[Ron Natalie]

Mxsmanic wrote:
> What are cowl flaps for, and how are they used? The name implies that
> they are some sort of aerodynamic control surface, but they don't
> appear to have any aerodynamic effects. In simulation, they are doors
> on the bottom of the engine nacelles that open for some unclear
> purpose (I see what looks like exhaust pipes or something inside).
> What do they do, and why do I have a control for opening and closing
> them? This is on a Baron 58, the aircraft I usually fly in
> simulation.
>

They control cooling air through the engine cowls. They are flap
shaped "valves" if you want on the outflow of the cooling air.
When open, you get more cooling air but that also means more
drag. In my plane, I can get another five to ten knots when
I close them. I take-off and climb with them open and close
them at cruise.

[Wade Hasbrouck]

"Mxsmanic" > wrote in message
...
> What are cowl flaps for, and how are they used? The name implies that
> they are some sort of aerodynamic control surface, but they don't
> appear to have any aerodynamic effects. In simulation, they are doors
> on the bottom of the engine nacelles that open for some unclear
> purpose (I see what looks like exhaust pipes or something inside).
> What do they do, and why do I have a control for opening and closing
> them? This is on a Baron 58, the aircraft I usually fly in
> simulation.
>
> --
> Transpose mxsmanic and gmail to reach me by e-mail.

They are not aerodynamic control surfaces... They are for regulating engine
temperature under certain power/speed combinations...

From Wikipedia...

If the aircraft is equipped with adjustable Cowl Flaps:

Cowl Flap Position Control - Cowl Flaps are opened during high power/low
airspeed operations like takeoff to maximize the volume of cooling airflow
over the engine's cooling fins.
Cylinder Head Temperature Gauge - Indicates the tempertaure of all cylinder
heads or on a single CHT system, the hottest head. A Cylinder Head
Temperature Gauge has a much shorter response time than the oil temperature
gauge, so it can alert the pilot to a developing cooling issue more quickly.
Engine overheating may be caused by:
Running too long at a high power setting.
Poor leaning technique
Restricting the volume of cooling airflow too much.
Insufficient delivery of lubricating oil to the engine's moving parts.

[tjd]

I went to a restaurant and they had these things called "flapjacks".
I'm so confused, are they some sort of aerodynamic device as the name
implies, or something you use to hold up the airplane while you change
those little black round things (Sorry I can't remember the name of
those!)? And what are they doing on a menu? How could I possibly
answer this question without annoying a large number of people? I
tried typing "flapjacks" into my Google simulator because I'm too
scared of the actual Google. But my computer crashed, imagine what the
real Google might have done!

--
Transpose my head and my butt to reach me by email.

[Rip]

Mxsmanic wrote:
> What are cowl flaps for, and how are they used? The name implies that
> they are some sort of aerodynamic control surface, but they don't
> appear to have any aerodynamic effects. In simulation, they are doors
> on the bottom of the engine nacelles that open for some unclear
> purpose (I see what looks like exhaust pipes or something inside).
> What do they do, and why do I have a control for opening and closing
> them? This is on a Baron 58, the aircraft I usually fly in
> simulation.
>
Plonk. Get a life.

[Mxsmanic]

Gary Drescher writes:

> http://stoenworks.com/Tutorials/Cowl%20Flaps%20&%20Engine%20C.html

Thanks, that's quite a comprehensive description.

It amazes me how much engine junk one is expected to worry about on
small aircraft. I'm also amazed that the engines are still
air-cooled.

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[Mxsmanic]

Ron Natalie writes:

> They control cooling air through the engine cowls. They are flap
> shaped "valves" if you want on the outflow of the cooling air.
> When open, you get more cooling air but that also means more
> drag. In my plane, I can get another five to ten knots when
> I close them. I take-off and climb with them open and close
> them at cruise.

Do you do this more or less routinely, or do you actually look at the
engine temperatures to see when to open or close them? I get the
impression that it's not a super-critical item except in a few
circumstances.

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[Aluckyguess]

That was funny.
"tjd" > wrote in message
oups.com...
>I went to a restaurant and they had these things called "flapjacks".
> I'm so confused, are they some sort of aerodynamic device as the name
> implies, or something you use to hold up the airplane while you change
> those little black round things (Sorry I can't remember the name of
> those!)? And what are they doing on a menu? How could I possibly
> answer this question without annoying a large number of people? I
> tried typing "flapjacks" into my Google simulator because I'm too
> scared of the actual Google. But my computer crashed, imagine what the
> real Google might have done!
>
> --
> Transpose my head and my butt to reach me by email.
>

[Gary Drescher]

"Mxsmanic" > wrote in message
...
> Gary Drescher writes:
>
>> http://stoenworks.com/Tutorials/Cowl%20Flaps%20&%20Engine%20C.html
>
> Thanks, that's quite a comprehensive description.

You're welcome. (It's the first page that comes up if you google "cowl
flaps".)

[John Gaquin]

"Mxsmanic" > wrote in message

> What are cowl flaps for, and how are they used?

A) Buy a book.

or

B) Pay a flight instructor for an hour, and ask him.

[Jim Macklin]

Don't forget augmenter tubes, pressure cowls, and the biggy,
how do you cool a jet engine?



"John Gaquin" > wrote in message
. ..
|
| "Mxsmanic" > wrote in message
|
| > What are cowl flaps for, and how are they used?
|
| A) Buy a book.
|
| or
|
| B) Pay a flight instructor for an hour, and ask him.
|
|

[Thomas Borchert]

Gary,

> You're welcome. (It's the first page that comes up if you google "cowl
> flaps".)
>

Yeah, but that would make it impossible to start a long-winded discussion
with real pilots about how backwards and dangerous the engines on their
planes are.

--
Thomas Borchert (EDDH)

[Jon Kraus]

5 or 10 knots? What are they freakn' barn doors or something? :-)
Sure your not fibbing?



Ron Natalie wrote:

In my plane, I can get another five to ten knots when
> I close them.

[Ron Natalie]

Mxsmanic wrote:
> Ron Natalie writes:
>
>> They control cooling air through the engine cowls. They are flap
>> shaped "valves" if you want on the outflow of the cooling air.
>> When open, you get more cooling air but that also means more
>> drag. In my plane, I can get another five to ten knots when
>> I close them. I take-off and climb with them open and close
>> them at cruise.
>
> Do you do this more or less routinely, or do you actually look at the
> engine temperatures to see when to open or close them? I get the
> impression that it's not a super-critical item except in a few
> circumstances.
>
I always open them before takeoff. With my old engine/cooling
setup it was really sensitive, so yes, I had to watch the the
temperature when closing them. On my new engine/cooling design
it runs pretty cool so I just shut them as a matter of routine
when I get to altitude. I do check the CHT and Oil Temp
periodically to make sure it's in the green.

[Neil Gould]

Recently, tjd > posted:

> I went to a restaurant and they had these things called "flapjacks".
> I'm so confused, are they some sort of aerodynamic device as the name
> implies, or something you use to hold up the airplane while you change
> those little black round things (Sorry I can't remember the name of
> those!)? And what are they doing on a menu? How could I possibly
> answer this question without annoying a large number of people? I
> tried typing "flapjacks" into my Google simulator because I'm too
> scared of the actual Google. But my computer crashed, imagine what
> the real Google might have done!
>
LOL!

This is the response I was looking for!

Neil

[Kev]

Thomas Borchert wrote:
> > You're welcome. (It's the first page that comes up if you google "cowl
> > flaps".)
> >
> Yeah, but that would make it impossible to start a long-winded discussion
> with real pilots about how backwards and dangerous the engines on their
> planes are.

It would also make it impossible to torture us with responses like that
one. Perhaps you could try adding to a discussion instead of dissing
it. Even "real" pilots argue over the safety of GA engines.

Some people are good at Googling. It could be argued that there's no
reason to ever again see questions and answers in any group, since
somewhere out there is a reply. But that wouldn't be any fun, as
everyone must have their say :-)

There's also a lot of people who can't spend much time Googling, since
they're still on dialup. They do things the old way, posting multiple
pre-made responses at once. I think that actually made for more
thought out discussions, since people couldn't just make knee-jerk
responses like you see around here.

Kev

[Neil Gould]

Recently, Kev > posted:

> Thomas Borchert wrote:
>>> You're welcome. (It's the first page that comes up if you google
>>> "cowl flaps".)
>>>
>> Yeah, but that would make it impossible to start a long-winded
>> discussion with real pilots about how backwards and dangerous the
>> engines on their planes are.
>
> It would also make it impossible to torture us with responses like
> that one.
>
Or, your response to Thomas', or my response to yours. ;-)

When the original topic's question can be thoroughly answered by reading
the first hit of a Google search, there really isn't much to add to the
"discussion". It's not like there will be conflicting opinions about this
question. So, might as well make it enjoyable for the rest of us who have
grown pretty tired of such pointless engagements.

Neil

[Kev]

Neil Gould wrote:
> Recently, Kev > posted:
> > Thomas Borchert wrote:
> >> Yeah, but that would make it impossible to start a long-winded
> >> discussion with real pilots about how backwards and dangerous the
> >> engines on their planes are.
> >
> > It would also make it impossible to torture us with responses like
> > that one.
> >
> Or, your response to Thomas', or my response to yours. ;-)

LOL. Exactly ;-)

> When the original topic's question can be thoroughly answered by reading
> the first hit of a Google search, there really isn't much to add to the
> "discussion". It's not like there will be conflicting opinions about this
> question. So, might as well make it enjoyable for the rest of us who have
> grown pretty tired of such pointless engagements.

Yep, if people would just let him get answered by those interested
enough to answer with a real reply, then the threads would be small and
we'd all be in good shape.

Regards, Kev

[John Theune]

Kev wrote:
> Neil Gould wrote:
>> Recently, Kev > posted:
>>> Thomas Borchert wrote:
>>>> Yeah, but that would make it impossible to start a long-winded
>>>> discussion with real pilots about how backwards and dangerous the
>>>> engines on their planes are.
>>> It would also make it impossible to torture us with responses like
>>> that one.
>>>
>> Or, your response to Thomas', or my response to yours. ;-)
>
> LOL. Exactly ;-)
>
>> When the original topic's question can be thoroughly answered by reading
>> the first hit of a Google search, there really isn't much to add to the
>> "discussion". It's not like there will be conflicting opinions about this
>> question. So, might as well make it enjoyable for the rest of us who have
>> grown pretty tired of such pointless engagements.
>
> Yep, if people would just let him get answered by those interested
> enough to answer with a real reply, then the threads would be small and
> we'd all be in good shape.
>
> Regards, Kev
>
But as has been pointed out so many times, often as not he then replies
with a statement about how he is right and the poster is wrong. His
answers are often wrong and if not corrected will be putting out bad
information in a forum that prides itself on correct information.

[Mark Hansen]

On 10/24/06 09:23, Kev wrote:
> Neil Gould wrote:
>> Recently, Kev > posted:
>> > Thomas Borchert wrote:
>> >> Yeah, but that would make it impossible to start a long-winded
>> >> discussion with real pilots about how backwards and dangerous the
>> >> engines on their planes are.
>> >
>> > It would also make it impossible to torture us with responses like
>> > that one.
>> >
>> Or, your response to Thomas', or my response to yours. ;-)
>
> LOL. Exactly ;-)
>
>> When the original topic's question can be thoroughly answered by reading
>> the first hit of a Google search, there really isn't much to add to the
>> "discussion". It's not like there will be conflicting opinions about this
>> question. So, might as well make it enjoyable for the rest of us who have
>> grown pretty tired of such pointless engagements.
>
> Yep, if people would just let him get answered by those interested
> enough to answer with a real reply, then the threads would be small and
> we'd all be in good shape.

Wow. If you really believe that, you simply have not been reading very many
of his posts.

>
> Regards, Kev
>



--
Mark Hansen, PP-ASEL, Instrument Airplane
Cal Aggie Flying Farmers
Sacramento, CA

[John Gaquin]

"Jon Kraus" > wrote in message news:pBm%g.17816

>5 or 10 knots? What are they freakn' barn doors or something? :-) Sure
>your not fibbing?

Sometimes cowl flaps can really disrupt airflow. On the DC3, the cowl flaps
have 3 positions: open, closed, and trail (controlled, btw, by a pair of
round valve handles that look for all the world like they were borrowed from
a steam locomotive). Open,they really stick out all around the cowling, and
in trail, they are pretty much closed, but will stay open a bit as needed.
Cowl flaps are an item on the pretake-off check. If you try to take off
with them in "open", it will set up a hell of a buffet.

[Dudley Henriques]

"John Gaquin" > wrote in message
. ..
>
> "Jon Kraus" > wrote in message news:pBm%g.17816
>
>>5 or 10 knots? What are they freakn' barn doors or something? :-) Sure
>>your not fibbing?
>
> Sometimes cowl flaps can really disrupt airflow. On the DC3, the cowl
> flaps have 3 positions: open, closed, and trail (controlled, btw, by a
> pair of round valve handles that look for all the world like they were
> borrowed from a steam locomotive). Open,they really stick out all around
> the cowling, and in trail, they are pretty much closed, but will stay open
> a bit as needed. Cowl flaps are an item on the pretake-off check. If you
> try to take off with them in "open", it will set up a hell of a buffet.

You wouldn't believe the drag on a P47 Thunderbolt with the cowls open.
Don't know about the D models, but on the N, you can easily use them as a
speed brake :-)) Also, taxiing with them open just about totally blinds you
in front of the airplane....not that the visibility is all that great in
front with them closed :-))
Dudley Henriques

[karl gruber[_1_]]

Some airplanes WILL NOT FLY with cowl flaps fully open. In the 50's there
was a Boeing Stratocruiser that took off from Boeing Field, Seattle. They
forgot to close the cowl flaps from ground to climb and ended up ditching
straight ahead in Elliot Bay, where the plane rests today.

http://www.ovi.ch/b377/articles/lady/

Karl



"John Gaquin" > wrote in message
. ..
>
> "Jon Kraus" > wrote in message news:pBm%g.17816
>
>>5 or 10 knots? What are they freakn' barn doors or something? :-) Sure
>>your not fibbing?
>
> Sometimes cowl flaps can really disrupt airflow. On the DC3, the cowl
> flaps have 3 positions: open, closed, and trail (controlled, btw, by a
> pair of round valve handles that look for all the world like they were
> borrowed from a steam locomotive). Open,they really stick out all around
> the cowling, and in trail, they are pretty much closed, but will stay open
> a bit as needed. Cowl flaps are an item on the pretake-off check. If you
> try to take off with them in "open", it will set up a hell of a buffet.
>

[Wade Hasbrouck]

For a minute I thought you were talking about the one that was ditched in
Elliot Bay in 2002, which was because they ran out of gas... They
relied/trusted the fuel gauges and didn't check the tanks, whi.ch were wrong
and they didn't have very much fuel. They later on fished that one out of
Elliot Bay and restored it, again.

But, I read the posting and sawa "In the 50's..." :-)

Sadly, there are lots of planes at the bottom of Elliot Bay and Lake
Washington.

"karl gruber" > wrote in message
...
> Some airplanes WILL NOT FLY with cowl flaps fully open. In the 50's there
> was a Boeing Stratocruiser that took off from Boeing Field, Seattle. They
> forgot to close the cowl flaps from ground to climb and ended up ditching
> straight ahead in Elliot Bay, where the plane rests today.
>
> http://www.ovi.ch/b377/articles/lady/
>
> Karl
>
>
>
> "John Gaquin" > wrote in message
> . ..
>>
>> "Jon Kraus" > wrote in message news:pBm%g.17816
>>
>>>5 or 10 knots? What are they freakn' barn doors or something? :-) Sure
>>>your not fibbing?
>>
>> Sometimes cowl flaps can really disrupt airflow. On the DC3, the cowl
>> flaps have 3 positions: open, closed, and trail (controlled, btw, by a
>> pair of round valve handles that look for all the world like they were
>> borrowed from a steam locomotive). Open,they really stick out all around
>> the cowling, and in trail, they are pretty much closed, but will stay
>> open a bit as needed. Cowl flaps are an item on the pretake-off check.
>> If you try to take off with them in "open", it will set up a hell of a
>> buffet.
>>
>
>

[Andrew Gideon]

On Tue, 24 Oct 2006 16:42:43 +0000, John Theune wrote:

> But as has been pointed out so many times, often as not he then replies
> with a statement about how he is right and the poster is wrong.

Then perhaps fewer people will reply to him, leaving fewer threads
discussing those replies.

- Andrew

[Jon Kraus]

But he has a Navion... I thought it would be similar to my Mooney...

John Gaquin wrote:

> Sometimes cowl flaps can really disrupt airflow. On the DC3, the cowl flaps
> have 3 positions: open, closed, and trail (controlled, btw, by a pair of
> round valve handles that look for all the world like they were borrowed from
> a steam locomotive). Open,they really stick out all around the cowling, and
> in trail, they are pretty much closed, but will stay open a bit as needed.
> Cowl flaps are an item on the pretake-off check. If you try to take off
> with them in "open", it will set up a hell of a buffet.
>
>

[Ron Natalie]

Jon Kraus wrote:
> But he has a Navion... I thought it would be similar to my Mooney...
>
They are pretty large doors, maybe 6x10" and the main cooling
intake is a few square feet. Closing them pretty much seals
up the cowl, only a little air escapes around the exhaust pipes.

[Mxsmanic]

karl gruber writes:

> Some airplanes WILL NOT FLY with cowl flaps fully open. In the 50's there
> was a Boeing Stratocruiser that took off from Boeing Field, Seattle. They
> forgot to close the cowl flaps from ground to climb and ended up ditching
> straight ahead in Elliot Bay, where the plane rests today.

The obvious question here is: Why would the cowl flaps open that far
if the plane wouldn't fly with them in that position? Unless it were
strictly for keeping the engine cool on the ground, I suppose (?).

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[swag]

They absolutely cause a 10knot difference in performance in a Skymaster
P337.
And if I recall they caused about 7 knots degradation in my 73 F33a Bo

Jon Kraus wrote:
> 5 or 10 knots? What are they freakn' barn doors or something? :-)
> Sure your not fibbing?
>
>
>
> Ron Natalie wrote:
>
> In my plane, I can get another five to ten knots when
> > I close them.

[Roger (K8RI)]

On 26 Oct 2006 15:05:08 -0700, "swag" > wrote:

>They absolutely cause a 10knot difference in performance in a Skymaster
>P337.
>And if I recall they caused about 7 knots degradation in my 73 F33a Bo

In my old Deb which has a number of speed mods and big engine they are
good for at least 10 knots.
>
>Jon Kraus wrote:
>> 5 or 10 knots? What are they freakn' barn doors or something? :-)
>> Sure your not fibbing?

It's not the flaps creating the drag. It's the air the let in around
the engine and out the bottom that adds the extra "cooling" drag.

>>
>>
>>
>> Ron Natalie wrote:
>>
>> In my plane, I can get another five to ten knots when
>> > I close them.
Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

[[email protected]]

Roger (K8RI) wrote:
> On 26 Oct 2006 15:05:08 -0700, "swag" > wrote:
>
> >They absolutely cause a 10knot difference in performance in a Skymaster
> >P337.
> >And if I recall they caused about 7 knots degradation in my 73 F33a Bo
>
> In my old Deb which has a number of speed mods and big engine they are
> good for at least 10 knots.
> >
> >Jon Kraus wrote:
> >> 5 or 10 knots? What are they freakn' barn doors or something? :-)
> >> Sure your not fibbing?
>
> It's not the flaps creating the drag. It's the air the let in around
> the engine and out the bottom that adds the extra "cooling" drag.


The air that goes into the cowling for cooling is air that isn't
used for thrust anymore, and when there's less thrust there's less
speed. With the cowl flaps closed, most of the air can't get into the
cowl openings and goes around instead, contributing to thrust.
There were some airplanes with well-designed cooling systems that
were able to recapture the lost thrust through the heating and
expansion of the cooling air. There was a discussion on one of these
groups several years ago about it. I think the P-51 was one of them.
The light airplanes we fly have cooling systems that are crude by
comparison.

Dan